engleski

Dental Arch Asymmetry in an Isolated Adriatic Community

Developmental stability reflects the ability of a genotype to develop in the same way under varying environmental conditions. Deviations from developmental stability, arising from disruptive effects of environmental and genetic stresses, can be measured in terms of fluctuating asymmetry, a particularly sensitive indicator of the ability to cope with these stresses during ontogeny. In an inbred Adriatic island population we expect dental arch fluctuating asymmetry (1) to be higher than in an outbred sample from the same island, and (2) within this population to increase with the level of inbreeding. Due to environmental stress, we also expect to find higher fluctuating asymmetry in the outbred island population than in an urban reference group from the same country. The material consists of 506 dental casts of 253 children (1) from the island of Hvar, and (2) from Zagreb, Croatia. Three-dimensional coordinates of 26 landmarks spanning the arches were digitized. The analysis partitions the asymmetry of the arch forms into components for directional and fluctuating bilateral asymmetry using the appropriate Procrustes method (geometric morphometrics). The results corroborated the hypotheses. Fluctuating asymmetry was found to be higher on the island than in Zagreb in all groups and in both jaws, and increased significantly with endogamy level in the lower jaw. There is no significant directional asymmetry in the Zagreb sample and likewise none in the upper jaw of the outbred island group, but significant directional asymmetry in both jaws of the inbred population and also in the lower jaw of the outbred island group. These results suggest an environmental as well as a genetic influence on dental arch asymmetry. Although the lower jaw expresses these two stresses almost additively, the upper jaw appears to be better buffered. The role of directional asymmetry as a potential indicator of craniofacial developmental instability clearly merits further attention.

geometric morphometrics; human isolates; endogamy; fluctuating asymmetry; directional asymmetry

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